When using a blood testing apparatus, a blood sample is normally taken by venipuncture. The blood is introduced into a small tube containing, for instance, 5 ml. From this tube, blood is sucked into a charging tube of the apparatus. Suction is stopped when the blood reaches a detector indicating that a sufficient amount of blood has been introduced into the apparatus. A well-defined volume of the blood sample, typically 25 .mu.l, is flushed by a defined volume, typically 5 ml, of a diluting liquid into a mixing vessel, where the sample is pre-diluted to typically 1:200. The diluted sample is further diluted 1:200 to a dilution ratio of 1:40000 for counting red blood cells and 1:1 to a dilution ratio of 1:400 for counting white blood cells.
When, however, a sample is taken from a finger tip, which is often practised when children are involved, the blood volume is small and is not sufficient for sucking into the apparatus for dilution as described above. Instead, a manual dilution procedure is practiced. The blood sample is manually collected in a small vessel and a defined volume thereof, typically 25 .mu.l, is introduced into a small diameter glass tube, i.e., a capillary tube often referred to as a "microcap ", or a "mini " or "micro " pipette, which sucks the sample by capillary action. The volume contained in the capillary tube is pre-diluted 1:200 by means of a separate dispenser. This pre-diluted sample is then sucked into the apparatus, whereupon final dilution takes place as when a venipuncture test is performed. However, this procedure is circumstantial in that it requires an extra manual step.
It would be desirable, thus, to simplify the procedure when making blood tests by way of finger tip puncture, and it is the object of the present invention to provide a method and a device that enable this.